Ejectors are used for conveying, compacting, or mixing tasks in rooms which man can no longer enter into because of the radiation load or other noxious influences prevailing in them, such as so-called "hot cells". As a rule, ejectors consist of two components only, namely, the casing forming a head and a diffuser as well as a working fluid nozzle housed in the casing. It is a particular advantage of such ejectors that they do not comprise any mechanically movable parts and, therefore, are subject to relatively little mechanical wear.
With such an ejector, a working fluid is blown by the working fluid nozzle through the interior of the head into the diffuser, which forms a long channel, narrowing at first and then widening again. A substance which is capable of flowing is sucked into the head through a suction connection and entrained through the diffuser. The preferred working fluid is vapor of such a nature that it is condensed in the diffuser, whereby the efficiency and suction head of the ejector are improved.
Under substantially constant marginal conditions the dimensioning of the bore in the working fluid nozzle in the first place determines the exhaust capacity and delivery obtainable by such an ejector. To vary those properties, therefore, the working fluid nozzle must be replaced by a different one of different dimensions. Moreover, the bore of the working fluid nozzle is subject to certain wear in the course of time so that it is most convenient to exchange it and replace it with a new one. However, the predominant disturbance occurring with an ejector is the plugging of the jet nozzle, and then it is mainly the bore of the diffuser which is obstructed.
Up to now manipulators have been used in rooms which are inaccessible to man for disassembling the entire ejector if disturbances of ejectors occurred that were no longer acceptable. The ejector thus has to be replaced by a new one or, perhaps, repaired outside the hot cell. That procedure, of course, is extremely difficult and time consuming. To overcome this disadvantage, it was proposed (DE-OS 28 10 767) that the working fluid nozzle of such an ejector be extended at its end remote from the diffuser by a bar passing through the wall of the hot cell.
In such a device, since the working fluid no longer can be fed, as customary, through the rear end of the working fluid nozzle, the working fluid nozzle comprises a working fluid chamber provided with a radial aperture opening into a working fluid space at the backside of the casing which forms the diffuser. The working fluid space is sealed with respect to the head, i.e., the space in which lies the open mouth of the working fluid nozzle. Further sealing is provided to the rear in the direction of the bar which extends the working fluid nozzle.
The bar which extends the working fluid nozzle can be displaced in the direction toward the interior of the casing when an obstruction of the diffuser occurs. The tip of the working fluid nozzle is pushed all the way into the mouth of the diffuser where its conical outer wall enters into sealing engagement with the diffuser inlet. Thus it is possible to use a sharp energy-rich working fluid jet to blow free the diffuser. At the same time, in this position the diffuser is blocked toward the suction connection. Therefore, it is possible to flush free the head space by a cleansing agent through a cleaning connection opening into the casing and disposed opposite the suction connection, without this cleansing agent getting into the diffuser and thus into the pressure outlet of the ejector. Thus, it is possible, for instance, to remove corrosions and deposits by corresponding chemicals and thereby clean the ejector again.
However, if such an ejector were to be used in regions in the interior of a hot cell which are removed from the walls thereof, it would be necessary to provide either a remote control drive or drive means operable by a manipulator to displace the working fluid nozzle until it abuts against the diffuser or to return it into its operating position. In any case, the resulting structure would be very complicated and, accordingly, susceptible to trouble and, for that reason, not suitable for erection in a hot cell. On the other hand, the cleaning effect obtainable by the known ejector is rather small. For instance, it is possible that not only the narrowest place of the diffuser bore becomes plugged but also, in addition, deposits form in the inlet zone of the diffuser bore and in the interior of the head region. When such deposits exist, the working fluid nozzle can no longer be driven into its cleaning position.